I use it as a substitute for crushed red pepper because it is not a nightshade, but it has a different flavor. It tastes a little lemony, and its hotness is more like black pepper than chili peppers.

One tip I learned belatedly: The seeds of Szechuan pepper are not good to eat - they're bitter and gritty. The part you're supposed to eat is the husk. It's a bit of a pain to separate them, but I got lucky when I bought a big bag of them because it only had the husks in it.